Hei, I have a one simple question which does not seem to be that simple as I cannot find any solution/answer: Is it possible to compare multiple survival curves in R with survdiff-function when there is interaction term involved in predictor variables (and this interaction is significant)? Example: survdiff(Surv(death,status)~treatment*gapsize) R is making "problems" with it ie.e. it does not want to perform the test. And all the examples I have found so far, may involve multiple predictor variables but in additive format (e.g. treatment+gapsize). If survdiff is not the way to go, are there any other solutions in order to compare statistically the curves i.e. if they differ significantly from each other? I would really appreciate if someone can answer! Cheers, Minna -- View this message in context: http://r.789695.n4.nabble.com/Survival-analysis-and-comparing-survival-curves-tp4414316p4414316.html Sent from the R help mailing list archive at Nabble.com.
Survival analysis and comparing survival curves
3 messages · R-girl, Bert Gunter, David Winsemius
DEAR R-girl:
On Thu, Feb 23, 2012 at 8:12 AM, R-girl <jhovinen at gmail.com> wrote:
Hei, I have a one simple question which does not seem to be that simple as I cannot find any solution/answer: Is it possible to compare multiple survival curves in R with survdiff-function when there is interaction term involved in predictor variables (and this interaction is significant)?
I have one simple answer. Get local statistical help. You do not understand the meaning of an interaction. -- Bert
Example: survdiff(Surv(death,status)~treatment*gapsize) R is making "problems" with it ie.e. it does not want to perform the test. And all the examples I have found so far, may involve multiple predictor variables but in additive format (e.g. treatment+gapsize). If survdiff is not the way to go, are there any other solutions in order to compare statistically the curves i.e. if they differ significantly from each other? I would really appreciate if someone can answer! Cheers, Minna -- View this message in context: http://r.789695.n4.nabble.com/Survival-analysis-and-comparing-survival-curves-tp4414316p4414316.html Sent from the R help mailing list archive at Nabble.com.
______________________________________________ R-help at r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
Bert Gunter Genentech Nonclinical Biostatistics Internal Contact Info: Phone: 467-7374 Website: http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm
On Feb 23, 2012, at 11:12 AM, R-girl wrote:
Hei, I have a one simple question which does not seem to be that simple as I cannot find any solution/answer: Is it possible to compare multiple survival curves in R with survdiff-function when there is interaction term involved in predictor variables (and this interaction is significant)?
I've never had a problem with survival failing to construct an interaction term.
Example: survdiff(Surv(death,status)~treatment*gapsize) R is making "problems" with it ie.e. it does not want to perform the test.
Is 'gapsize' a numeric vector rather than a factor?
And all the examples I have found so far, may involve multiple predictor variables but in additive format (e.g. treatment+gapsize). If survdiff is not the way to go, are there any other solutions in order to compare statistically the curves i.e. if they differ significantly from each other?
Without a better description of the data layout (say using hte str() function) and the code you have used so far, the words "the curves", the indefinite pronoun "they" and the phrase "each other" will remain far too nebulous for further comment.
I would really appreciate if someone can answer!
Only if "someone" can provide the information requested in the Posting Guide.
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
David Winsemius, MD West Hartford, CT